Method and apparatus for pointing tubes

ABSTRACT

Method and apparatus for forming a generally cylindrical point on a tube by first flattening the tube from at least three sides to a polygonal cross section while forming curved sections between the flat sides, and then progressively contracting the tube to bring the curved sections together while buckling the flat sides inwardly into loops that are flattened inside the point. At least three die shoes arranged around a die recess in alternately overlapping relation have flat inner faces with an elongated lip along one side for shaping the curved sections, and also have flat, inclined bevels for shaping the transition zone of the tube during pointing, each bevel having a part-conical lip on one side for the final shaping of the transition zone to a conical shape. One actuating arrangement utilizes a mutual camming action to move all die shoes simultaneously at the same rate to maintain the point on a preselected axis, while a simpler form displaces the axis during pointing.

United States Patent [151 3,695,087

Tuberman 1 51 Oct. 3, 1972 54] METHOD AND APPARATUS FOR 397,343 8/1933Great Britain ..72/367 POINTING TUBES 35,625 4/1955 Poland ..72/402 [72]Inventor: St Primary Examiner- Charles W. Lanham V w AssistantExaminer-Gene P. Crosby [22] Filed: Aug. 26, 1970 Attorney-Fulwider,Patton, Rieber, Lee & Utecht Method and apparatus for forming agenerally cylin- [52] US. Cl "72/402, 72/452 drical point on a tube byfirst flattening the tube from [51] Int. Cl. ..Bzld 41/04 at least threesides to a polygonal cross section while Field of Search 367,36913998400 forming curved sections between the flat sides, and 72/410,463, 470, 472; 5 then progressively contracting the tube to bring thecurved sections together while buckling the flat sides [56] ReferencesCited inwardly into loops that are flattened inside the point. At leastthree die shoes arranged around a die recess UNITED STATES PATENTS inalternately overlapping relation have flat inner faces 3,478,565 11/1969Schenk ..72/399 h an elongated p along one side for Shaping the2,589,142 3/1952 Rotheroe ..72/400 curved Sections, and also have flat,inclined bevels for 3,068,929 12/1962 Rowell ..72/400 Shaping thetransition Zone of the tube during p 3 292,414 12/1966 Goeke ..72/402each bevel having a Pan-conical P on One Side 3:4l7,598 12/1968 Valente..72/383 for h final Shaping of the transition 99 a 3,509,785 5/1970Fuchs ..72/347 shape: one i arrange? l a mutual cammmg action to moveall d1e shoes simultaneously FOREIGN PATENTS QR APPLICATIONS at the samerate to maintain the point on a preselected h'l l f d' 1 th 372,5435/1932 Great Britain ..72/367 2239:; e a Slmp er om aces e was durmg449,558 9/ 1927 Germany ..72/402 1,035,352 4/1955 Germany ..l8/DlG. 5 16Claims, 27 Drawing Figures PATENTEB B81 3 1 72 SHEEI 3 0F 3 BACKGROUNDOF THE INVENTION This invention relates to the fomiing ofreduceddiameter end portions on tubes for use in gripping the tubesduring an operation such as drawing through a die. Such reduced-diameterend portions (called points although they typically are generallycylindrical or have some other blunt-ended shape) are necessary becausethe original tubing to be drawn through the die has a larger outsidediameter than the diameter of the die, and also to provide a portion ofthe tube that can be gripped securely to apply the drawing force.

Tube pointing machines of various types are known and have been used bythe trade. For example, U.S. Pat. No. 3,292,414 shows an apparatus forswaging points with a plurality of arcuate reciprocating die segmentswhich compress a tube as the arcuate faces of the dies are pressedtogether around the tube. Rotary swaging also has been used. Inanother,. somewhat similar approach, represented by U.S. Pat. No.3,073,374, a tube is positioned'between two dies havingsemi-cylindrical, concave faces and is pinched and pleated from oppositesides before the semi-cylindrical dies are closed around the tube.

In still another approach, shown in U.S. Pat. No. 3,068,929, a tube ispositioned over an open-sided, part polygonal recess and then forcedinto the recess by two rams which, when moved toward the open side ofthe recess, compress the tube into the recess and cooperate therewith toform a regular polygonal cavity in which the tube is collapsed andcompacted to the desired shape. A similar result is obtained by thepointer shown in U.S. Pat. No. 3,417,598 in which four dies arrangedaround the end of a tubeare formed with interleaved flat-edged ribswhich permit the dies. to' be moved -together to crush the end portionof the tube into a point.

While these and other known pointers are capable of producing usablepoints on tubes, all of the pointers presently available are subject toone or more deficiencies that have prevented the achievement of optimumresults. Specifically, many of the machines produce an excessively highnoise level as an incident to the pointing operation, or require rathercomplicated and difficult-to-maintain machinery. More importantly,despite claims that points can be formed completely in one stroke, itoften is necessary to repeat the forming stroke several times in orderto obtain a proper point, probably because most of the die systemsinherently include gaps into which the metal can be displaced duringpointing. At the same time, it is difficult, if at all possible, toobtain uniformity in point diameters while maintaining the pointsconcentric with the tubes.

The configuration of the transition zone between the point and the bodyof the tube is particularly important from the standpoint of performanceof the tube during subsequent drawing operations. If the tube is foldedwith nonuniform convolutions or distinct creases, particularly in thetransition zone, as is common in some of the prior pointers, stressrisers are set up and can result in cracks which propagate down thetube. during the drawing operations.

Moreover, many tube materials are notch sensitive, that is, tend tobreak under stress wherever a notch or groove has been fomied duringpointing. Thus, any pointer which notches the tube during pointing,particularly in or around the transition zone, produces a likelihood offailure during subsequent operations. Of course, ruggedness, durabilityand relative simplicity of construction, as well as economy inconstruction, operation and maintenance, are primary objects of anyproduction machine, and certain of the prior art machines, such as thoserequiring interleaved ribs, are deficient in these respects.

SUMMARY OF THE INVENTION The present invention resides in an improvedtube pointer which produces superior and uniform points in a novelmanner by positively guiding and controlling the bending of the tubematerial at all times, both in the zone of the point and in thetransition zone, while eliminating gaps in the die apparatus that couldresult point precisely concentric with the tube, thereby avoiding thedisadvantages or prior pointers.

To the foregoing ends, the pointer includes a die having at least threedie shoes that are arranged around and define an open-ended die recessof generally polygonal cross section and are interfitted to permit theshoes to move inwardly and outwardly, radially of the tube, to contractand expand the recess, the shoes having substantially flat inner workingfaces which form the tube first into a generally polygonalcross-sectional shape as the shoes move inwardly to contract the recess.The shoes also include means for shaping the tube between the sides ofthe polygonal cross section into arcuate sections so that continuedinward movement of the shoes progressively shortens the sides of thepolygonal cross section to buckle and fold the sides inwardly whilemoving the arcuate sections toward each other, finally squeezing thearcuate sections substantially together into a generally cylindricalpoint with the buckled portions formed as flattened loops within thepoint.

Controlled formation of the transition zone of the tube is accomplishedby substantially flat bevels on the die shoes which have the same slopeaway from the working faces as the desired angle of the cone of thetransition zone, the bevels also having means thereon for closingconically around the transition zone as the arcuate sections of thepoint are brought together. The controlled buckling of the point zoneand the controlled sinking of the bevels into the tube cooperate to formuniform folds or convolutions inthe transition zone with soft creasesthat flare from the point toward the tube into wide and gently roundedends at the junction with the tube.

To permit such progressive contraction of die shoes having flat workingfaces, the shoes are arranged in alternately overlapped relation so thatan edge of one shoe slides along the working face of one adjacent shoe,while an edge of the other adjacent shoe slides along the Working faceof the first shoe. The illustrative arcuate shaping means for the pointcomprise fillets overlying the junctions between the working faces andhaving concave inner surfaces constituting longitudinal sections of acylinder, and the corresponding means for the transition zone compriselongitudinal sections of a cone overlying the junctions between thebevels.

The concentricity of the point and the tube are maintained in thepreferred forms of the invention by moving each die shoe toward the axisof the tube at the same rate, and this is accomplished with a singleactuator which shifts one of the'die shoes toward the axis at thedesired rate while the remaining shoes are cammed inwardly at the samerate in response to the driving force applied by the actuator. Thus, thearcuate sections of the shoes can be maintained concentric with the tubeat all stages of the pointing operation.

Other objects and advantages of the invention will become apparent fromthe accompanying detailed description, taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS of a'tube pointer embodying the novelfeatures. of the present invention, with a length of tubing in positionfor insertion into the pointer, a representative actuator partiallybroken away and shown in cross section, and parts of the pointer shownpartly in broken lines for clarity; v

FIG. 2 is an enlarged fragmentary cross-sectional viewof the pointer inFIG. 1, taken substantially along the line 22 thereof, after the tube tobe pointed has been inserted in the open die;

FIG. 3 is a view similar to FIG. 2 showing the pointer andtube after thedie has been closed to form the point; g

. FIG. 3A is an enlarged fragmentary cross section taken substantiallyalong the lines 3A3A of FIG. 3;

FIG. 4 is an enlarged fragmentary perspective view of one of the dieshoes of the pointer;

FIG. 5 is a fragmentary plan view of the die shoe of FIG. 4;

FIG. 6 is an enlarged fragmentary perspective view of a pointed tube;

FIG. 7 is an enlarged end view of a representative tube with the dieshown schematically at the beginning of the pointing operation;

FIG. 8 is a view similar to FIG. 7 showing the first stage of bending ofthe tube during the initial closing of the die in which the tubeisgenerally polygonal in cross section and the flat sides are connected byarcuate sections;

FIG. 9 is a similar view showing the next stage of bending as the wallsof the tube begin to buckle during shortening of the flat sides;

' FIG. 10 is a similar view showing the next stage as the bucklingcontinues and loops begin to form;

FIG. 1 l is a similar view showing another stage as the loops areflattened and compressed and the arcuate sections are brought together;

, FIG. 12 is a cross-sectional view similar to FIG. 2 on a somewhatreduced scale illustrating an alternative form of the pointer havingfour die shoes, the die being open;

FIG. 13 is a view similar to FIG. 12 with the die closed on a tube;

FIG. 14 is an end view of the pointer in FIG. 12 with a front coverplate thereof partly broken away;

FIGS. 15 to 19 are sequential views similar to FIGS. 7 to 11illustrating the bending of a tube to a point with the pointer of FIGS.12 to 14;

FIGS. 20 and 21 are views similar to FIG. 14 illustrating an alternativemanner of support and actuation of the die shoes of a four-shoe pointer;

FIG. 22 is a fragmentary perspective view of a die shoe of the type usedin the pointer of FIGS. 20 and 21;

FIGS. 23 and 24 are fragmentary views showing the arrangement of dieshoes in a pointer having six die shoes, FIG. 23 showing the openposition and FIG. 24 showing the closed position; and

FIGS. 25 and 26 are fragmentary views similar to FIGS. 23 and 24 butshowing the arrangement of die shoes in a pointer having eight shoes.

DETAILED DESCRIPTION As shown in the drawings for purposes ofillustration, and with specific reference to FIGS. 1-11, the inventionis embodied in a tube pointer 10 for forming a reduced diameter endportion or point 11 (see FIG. 6) on a tube 12, for subsequent use ingripping the tube and pulling it through a drawing die (not shown) for aconventionalpurpose such as redrawing of tubing where the diameter is tobe reduced, the wall thickness is to be changed, and the like, to obtainthe different sizes, shapes and other characteristics required inindustry. The point may be inserted through such a die and then grippedin a suitable chuck with which the drawing force is applied.

In general, the pointer 10 includes a pointing die 13 formed by a set ofdie shoes which are arranged around and define a recess 14 that is openat one end to receive the end of the tube 12 to be pointed. The die setis mounted in a case including a top member 15 above the die shoes, sidemembers 17 depending from opposite edges of the top member, and a bottommember 18 below the shoes. Herein, the case is supported between a pairof spaced front and rear guides 19 and 20 upstanding from and bolted toa suitable base 21, such as a table, and connected by bars 22. Each ofthe illustrative guides has upright flanges 23 (FIG. 1) which straddlethe front and rear edges of the side members 17 and support the latterand the top member 15 for up and down motion, toward and away from thetable 21 and the bottom member 18. This up and down motion is used toexpand and contract the die recess 14 by moving the die shoesalternately outwardly, away from each other, into the open conditionshown in FIGS. 1 and 2, for insertion of a tube 12 in the pointer 10,and then inwardly toward each other into the closed condition (FIG. 3)to compress the portion of the tube within 7 the die recess and form thereduced diameter point 11 thereon. It should be understood, however,that this is only oneof various arrangements that may be used to supportthe die.

In accordance with the primary aspect of the present invention, at leastthree die shoes 24, 25 and 26 are arranged around the die recess 14 andhave inner working faces 27 that initially define the recess with agenerally polygonal cross section, and are fitted together to permit theshoes to be moved simultaneouslyinwardly, toward each other, to bend thetube initially to the polygonal cross section and then to contractthecross section progressively as such movement continues; In addition, thedie shoes have curved surfaces 28 shaping the portions of the tubebetween the sides of the polygonal cross section into curved sections,which are squeezed progressively toward each other as the die shoes areclosed. Accordingly, the continued shortening of the sides, accompanyingthe squeezing of the curved sections toward each other, causes theportions of the tube between the curved sections to buckle inwardly in acontrolled and predictable manner, forming loops which are flattened andcompressed within the point as the curved sections are brought togetherto form the periphery of the point.

' In its broader aspects, the invention also contemplates the control ofthe formation of the transition zone 29 of the tube 12 in a novelmannerwhere the outside diameter increases from that of the point 11 tothat of the body of the tube. For this purpose, each die shoe 24, 25, 26has a bevel 30 that is inclined outwardly and forwardly from the frontof the working face 27 at a selected angle relative to the axis of thetube. These bevels sink progressively into the tube from all sides asthe point is formed, and insure that the folds or convolutions(indicated generally at 31 in FIG. 6) in the transition zone are formeduniformly and without objectionable creases or notches. Finally, curvedsurfaces 32 between the bevels close conically around the transitionzone as the curved surfaces 28 close around the remainder of the point.

In the illustrative embodiment shown in FIGS. 1-5,

each die shoe 24-26 is shown as having the flat working face 27 disposedin a plane parallel to the axis of the tube 12, the three working facesbeing identical and cooperating to define the recess 14 with the generalcross-sectional shape of an equilateral triangle, as shown most clearlyin FIG. 2. The three shoes are arranged in alternately overlappingrelation, each having one side edge portion 33 which abuts slidablyagainst an extension of the working face of an adjacent shoe on oneside, while the corresponding side edge portion 33 of the other shoeabuts slidably against an extension of the working face of the firstshoe. Thus, all three shoes can be moved simultaneously inwardly towardthe tube axis in mutually sliding, gap-free relation. 5 Each side edgeportion 33 of a shoe that overlaps the working face 27 of the adjacentshoe herein is formed with an inwardly projecting, longitudinal lip 34having an arcuate inner side of concave curvature constituting thecurved surface 28 for shaping the curved sections of the tube, thissurface preferably being concentric with the tube and tangent to theworking face 27 of the shoe on which it is formed, and also tangent tothe working face 27 of the shoe against which the lip slides. Ideally,the arcuate surface might terminate in a knife edge at 35, but for thepractical purpose of minimizing the likelihood of breakage, this edgepreferably is blunted.

As shown most clearly in FIGS. 3A and 4, the bevels are simply flatsurfaces disposed at suitable forwardly and outwardly inclined angleswith the axis of the tube, for example, five to forty degrees, dependingupon the desired angle of the transition zone. On one side of I eachbevel is a flared lip 36 constituting an extension of the associated lip34 and having a concave inner side which preferably is a section of acone-and constitutes the surface 32 for shaping the tube in the.transition zone. The free edge of this lip preferably is blunted fordurability and isin the same plane as the edge of the lip 34.

The actuator of the pointer 10, which may take various forms, moves allof the die shoes simultaneously inwardly relative to each other towardthe axis of the tube 12 (which may beeither stationary or movable)thereby to close the die 13. During such closing movement, theoverlapping side edge portions 33 slide along the working faces 27 ofthe adjacent shoes while the working facesthemselves remain parallel tothe tube axis. Thus, the working faces first are pressed against thesides of the tube (three sides as in FIG. 7) in tangent relationtherewith along three longitudinal lines 37, and then begin to flattenthe sides of the tubeprogressively toward the triangular condition shownin FIG. 8. Such flattening is accompanied by initial sinking of thethreebevels 30 into the tube in angularly spaced relation around the portionof the tube within the flared end portion .of the die recess 14 that isdefined by the bevels. I

As closing of the die 13 continues, the tube 12 is formed to the shapeshown in FIG. 8 with three flat sides 38, and the longitudinal portionsof the tube between these flat sides are shaped into arcuate sections 39which nest firmly against the inner surfaces .28 of the lips 34. Afterthe die. reaches the condition shown in FIG. 8, further inward motion ofthe shoes squeezes the arcuate sections 39 radially inwardly andprogressively shortens the exposed portions of the working faces. Theflat sides 38 of the tube, being confined and backed against outwardbulging, begin to buckle inwardly, as shown at 40 in FIG. 9, and to formloops'as shown at 41 in FIG. 10. Apparently because there is effectivetangential travel ofthe working faces 27 as the die 13 is closed, theloops 41 thus formed are not directed exactly toward the axis of thetube, as might be expected. Instead, as illustrated in FIG. 10, eachloop is offset slightly from center so that continued crushing of thetube results in flattening of the loops in an offset, pinwheel fashionas shown in FIG. 11, thus producing a general symmetry or uniformity inthe cross-sectional configuration of the point. Closing of the die canbe terminated at any selected stage after the generally cylindricalpoint 1 1 has been formed, and, of course, can be continued beyond thecondition shown in FIG. 11 if a denser point is desired. In fact, withsufficient actuating pressure and appropriately formed die shoes, thepoint can be crushed to an essentially solid'rod and even extended inlength.

The loops 41 shown in FIG. 10 extend forwardly beyond the working faces27 and along the bevels 30, while the arcuate sections 39 extendforwardly and flare outwardly along the concave surfaces 32 constitutingsections of a cone. Thus, each transition convolution 31 (FIG. 6) isformed between two .arcuate sections of the tube that are controlled bythe conical surfaces, and it has beenfoundthat a rounded crease forms atthe bottom of the convolution and spreads progressively as theconvolution flares, being broadly rounded short of thelarger end of thetransition zone 29. As closing of the die is completed, the part-conicalsurfaces 32 come together into the desired full-conical shape to formthe transition zone to that shape..The closed, conical condition isshown most clearly in FIG. 3A, and also in FIG. 21 with regard to afour-shoe form of the pointer, hereinafter described in detail.

The-preferred manner of actuation of the pointer is the camarrangement-illustrated-in FIGS. 2 and 3 wherein it will be seen thatthe upper die shoes 24 and 26 are arranged generally in the shape of aninverted *V with inclined, upwardly facing outer sides 42 and 43parallel to the working faces 27 of the shoes and nested againstsimilarly inclined, downwardly facing surfaces 44 and 45'o'n theunderside of the top member of the case. The third die shoe 25 isgenerally triangular in shape and has an outer side 47 that is inclinedupwardly and to the left, and the' overlapped side edge .33 is-inclineddownwardly and to the right beyond the overlapping portion of theworking face 27 of the shoe 24. Rollers 48 are disposed between theinclined outer side 47 and an inclined, parallel upper surface 50 of thebottom member 18, thus supporting the lower die shoe 25 for movementupwardly and to the-left along the inclined surface 50 of the bottommember.

A coiled extension spring. 51 is stretched between two pins 52 and 53respectivelymounted in a recess 54 in the bottom member 18 and a recess55 in the lower die shoe 25, thus urging the shoe downwardly toward theposition shown in FIG. 2 and holding it firmly against the rollers 48;which may be maintained in spaced parallel relation by rack-and-pinionmechanisms 57 at their ends, as shown in FIG. 1. A similar spring 58 forholding the upper right die shoe 24 against the surface 44 is stretchedbetween pins 59 and '60 .on the top member 15 and the shoe, although itwill be seen that this shoe does not move relative to the upper memberduring actuation of the pointer. The

spring merely holds the die shoe firmly-in place against the surface 44and formsa releasable connection facilitating changing of the die. 1

The die shoe 26 may be similarly spring positioned, but preferably iscontrolled by a hydraulic cylinder formed by a blind bore 61 whichparallels the inclined surface 45 of the top member and telescopinglyreceives the lower end portion of a plunger 62 that is formed with alongitudinal through passage 63. This passage communicates at its lowerend with the bore 61 and at its upper end with a conduit 64 forreceiving fluid under pressure from an external source (not shown)through a fitting 65. This cylinder forms, in effect, a hydraulic springwhich returns the shoe 26 and the top member l5.to the positions shownin FIG. 2 to open the die 13 after each pointing operation.

' advantageous.

With the foregoing arrangement, the parts are I disposed in thepositions shown in FIG. 2 prior to each pointing operation, and a tube12 may be inserted in the open die recess 14 in the manner shown, withsufficient clearance around the tube to permit easy insertion. Ifdesired, a tube guide (not shown) may be the bottom member 18-, thusforcing the right upper die shoe 24 downwardly along the right side ofthe lower die shoe 25. As the right shoe slides along the lower shoe,the abutting inclined surfaces 33'and 27 of the shoes cooperate to camthe lower shoe to the left, and the upwardlyinclined surface 50 of thebottom member 18 simultaneously guides the lower shoe upwardly andinwardly at a ratedetermined by the slope of the surface 50. At the sametime, this upward motion of the lower shoe is transferred to the loweredge 33 of the left shoe 26 through the overlapped sides .of the twoshoes, and is combined with the downward motion of the top member 15 toproduce an inward (to the right) motion of the left die shoe at a ratedetermined by the slope of the inclined surface 45 and the rate ofmovement of the left shoe along this surface.

Accordingly, with properly correlated slopes on the various camsurfaces, the three die shoes 24-26 are moved simultaneously and at thesame rate toward the axis of the tube 12. Termination of this closingmovement can be controlled in various ways, for example, by one or morelimit switches (not shown) actuated in response to movement of the dieshoes to selected positions, the limit switches preferably beingadjustably positioned for selective variation of the point oftermination. The same switching arrangement that terminates the closingstroke also can automatically initiate the following opening stroke.

During opening of the die recess 14, the three shoes 24-26 movereversely along the paths followed during FIRST ALTERNATIVE EMBODIMENT(FIGS. I 12-19) It has been stated that at least three die shoes arebelieved to be necessary in order to define a gap-free die recesscapable of being closed around a tube in accordance with the presentinvention. It should be emphasized, however, that the invention is notlimited to the use of three die shoes, and that, in fact, differentcircumstances may make the use of four or more shoes Since each die shoeproduces one fold or convolution in the tube in, and adjacent to, thepoint, changes in the number of shoes will result in different numbersand angular spacings of the convolutions. With tubes having walls with arelatively high thickness-to-diameter ratio, it is relatively difficultto buckle and fold the tube wall, so the use of a lesser number of shoeswill form the folds farther apart, angularly, around the tube and insurethat the wall sections will buckle inwardly from the polygonal stagerather than feeding peripherally around the inner surfaces of the die.For tubes having walls with a relatively low. thickness-todiameterratio, a greater number of die shoes are used to provide better controlof the relatively easy-to-fold tube walls.

In the pointer 70 shown in FIGS. 12-14, in which some corresponding,generally similar parts are indicated by corresponding reference numbersit will be In addition, as shown in FIG. 14, each die shoe 71-74 has abevel 30 from the forward end of the working face 27 to the front sideof the shoe, and each bevel merges smoothly with a part conical surface32 for shaping the transition zone 29- of the tube as the die is closed,forming the full conical surface around the tube -as can be seen in thesimilar form shown in FIG. 21.

The four die shoes 71-74 of FIGS. 12-14 are mounted and actuated insubstantially the same way as the three shoes in FIGS. 1-5, beingmounted in a case including a fixed bottom member 18, two upstandingside plates 17 which in this instance are fastened to the side edges ofthe bottom member, and a top member which is movable vertically betweenthe side plates. A

- ram 67 engages the top member to apply the force necessary to push thetop. member down and close the die around the tube 12, and a front plate75 is bolted to the bottom member and the side plates to close the frontof the case except for an aperture 77 (FIG. 14) formed therein to admitthe tube into the die recess 14.

. In this instance, the upper right die shoe 71 is detachably connectedto the top member 15 by a spring 78 and remains stationary duringactuation of the pointer 70, as did the shoe 24 in the first form, andthe lower right shoe 72 is slidable horizontally across the top surface50 of the bottom member in response to the camming action of thedownwardly and rightwardly inclined working face 27 of the upper rightshoe 71 on the abutting inclined side 33 of the lower right shoe. Aspring 79, stretched between the shoe and the adjacent side plate 17,yields during closing of the die and then returns the shoe to the rightwhen the closing force is relieved.

The lower left shoe 73 slides vertically along the left side plate 17 inresponse to the camming action'of the the inclined face 27 of the lowerright shoe 72 on the abutting inclined side 33 of the lower left shoe,and is urged yieldably toward the bottom member 18 by av 73, this faceabutting against the inclined edge 33 of the 1 generally rectangularinitial cross section with four sides 81 (FIG. 16.) joined by fourarcuate sections 82. This is followed by the'bucklin'gof the four sidesat 83 (FIG. 17), the formation of loops 84. (FIG.. 18) which areslightly offsetfrom center, and the collapse of the loops into thegenerally cylindrical point 85 (FIG. 19). From this collapsed condition,the point may be further compressed to a smaller diameter and greaterdensity, as desired. Of course, the formation of the transition zone ofthe tube follows the same procedure as before,

with the addition of one fold or convolution.

SECOND ALTERNATIVE EMBODIMENT (FIGS.

The pointer 90 shown in FIGS. 20 and 21 is similar to the firstalternative embodiment in that it has four die blocks 71-74(corresponding reference numbers being used in bothof these forms, whereapplicable), but in this case the closingof the die results indisplacement of the axis of the die recess 14 and-the tube point,downwardly in parallel from the original position. Thus, this pointer issuited for use under circumstances which permit the tube to be movedduring the pointing operation so as to follow the movement of the pointand remain at least generally coaxial therewith.

As will be seen most clearly in FIG. 21, the configu- I upper left shoe.A blind bore 61 is formed in the upper virtually the same as in FIGS.12-14. The shoes may be identical in shape, however, with outer sides 91parallel to the working faces 27 and with opposite end surfaces 92 and93 in planes that are perpendicular to the inner and outer surfaces.Actuating plates 94 are fastened, as by bolting, to the outer sides 91with one projecting end portion 94a of each plate overhanging'the endsurface 93 of. an adjacent shoe, inspaced parallel relation therewithwhen the dieis open (FIG. 20). Coiled compression springs 95 aredisposed between these overhanging portions and the adjacent endsurfaces to urge the die shoes toward the-open positions. Herein, thesprings are held in place by bores 97 which extend into the shoes sothat the springs are compressed between the actuatingplates and the endsof the bores. Thus, the springs urge the plates 94 away from the ends ofthe shoes, and thereby urge the die shoes toward the open conditionshown in FIG. 20.

The two lower shoes 72 and 73 are nested in a V- shaped groove or notchin the bottom member 18 with the associated actuating plates 94 restingagainst the walls of the notch, and the two upper shoes 71 and 74 aresimilarly nested in an inverted V-shaped notch in the underside of thetop member 15. In this instance, the side plates 17 are fastened to thetop member and extend downwardly along, and slide against, the sides ofthe bottom member.

As the top member 15 is forced downwardly by the ram 67, the two upperdie shoes 71 and 74 are forced downwardly toward and against the tube12, the upper right shoe 71 moving substantially straight down andcamming the lower right shoe 72 downwardly to the left, deeper into thelower notch. As this happens, the lower left shoe 73 remainssubstantially stationary and the upper left shoe 74 is cammed upwardlyto the right and deeper into the upper notch. I

Accordingly, the die is closed as before, but the axis of the die recessmoves progressively lower during such operation.

springs retum the die shoes to the open condition of FIG. 20. Theactuating plates 94 prevent a combined rotation effect of the die shoesthat could-be present if the springs were to bear against the surfacesof the notches in the top and bottom members.

" ADDITIONAL ALTERNATIVE EMBODIMENTS '(FIGS. 23-26) The schematic viewsin FIGS. 23-26 are included. to illustrate diearrangements for largernumbers of die shoes, six in FIGS. 23 and 24 and'eight in FIGS. 25 and26. It will be seen that the initially exposed portions of the workingfaces 27 become progressively shorter, in proportion, as the number ofdie shoes is increased, thus forming initial folds of shorter angularextent, and the arcs of the arcuate surfaces 28 are similarly changed asthe final cylinder is divided into a larger number of longitudinalsections that are distributed around the die as parts of the die shoes.

.From the foregoing, it will be seen that the present invention providesa novel apparatus for forming reduced diameter portions or points ontubes, and uses a similarlynovel method of reducingthe diameter to asubstantially similar point. In each embodiment illustrated anddescribed, the alternately overlapping die shoes are movable in gap-freerelation from an open position in which the flat inner working faces ofthe shoes define a die recess of regular polygonal shape with curvedsurfaces between the flat sides, thus forming the tube to the samepolygonal shape with curved longitudinal sections as an incident to theinitial closing movement of the die shoes. Moreover, continued closingmovement in each case progressively shortens the flat sides whilesqueezing the curved sections toward each other, causing the flat sidesto buckle inwardly and form loops that may be flattened in a relativelyuniform manner within the point.

The result is a die apparatus and pointing method which produce improvedpoints ,in a highly effective manner, with a relatively simple diestructure of competitive initial cost and relatively rugged and durableconstruction, and with a smooth and continuous stroke that normally iseffective to form the point in a simple, rapid and quiet operation.Accordingly, the present invention avoids disadvantages that have beeninherent in prior pointers, while forming a controlled point withoutnotches, creases or other irregularities that could. interfere withproper performance in a later Iclaim: .1. A tube pointer having, incombination:

a case; a die mounted in said case and comprising at least three dieshoes arranged in alternately overlapped relation around, and defining,an open-ended recess for receiving one end portion of a tube to bepointed; each of said die shoes .having a flat inner working faceforming one side of said recess, a side surface in sliding relation withan extension of the working face of a first adjacent die shoe, and anextension of its working face-in sliding relation with the side surfaceof a second adjacent die shoe whereby said shoes are movablesimultaneously inwardly from an open position toward a closed positionand then back outwardly toward said open position to contract and expandsaid recess; a bevel on each of said shoes inclined outwardly from theworking face thereof toward said open end; an elongated first lipextending along the side of each working face adjacent the side surfacethereof that slides along the working face of an adjacent block, each ofsaid lips having a curved inner surface generally tangent to both of theadjacent working faces and curved about the axis of a tube centered insaid recess; and a second lip constituting an extension of said firstlip on each of said shoes along one side of the bevel thereon, each ofsaid second lips having an inner surface of generally conical curvatureflaring toward said open end and generally tangent to both of theadjacent bevels, whereby said die shoes are movable progressivelyinwardly from said open position to contract said recess about a tube,bend the tube first to a flattened, generally polygonal cross sectionwith curved sections between the flattened wall portions, progressivelycontract the tube polygonally to cause the flattened wall portions tobuckle inwardly, and finally bring the curved sections together to asubstantially cylindrical point while shaping the tube conically betweensaid second lips.

2. A tube pointer as defined in claim 1 further including meansfor'moving all of said die shoes simultaneously inwardly at the samerate and maintaining the point on a preselected axis as it is formed.

3. A tubepointer as defined in claim 2 in which said moving meansincludes actuating means for shiftingat least one of said shoes inwardlyat a selected rate, and camming means responsive to movement of saidactuating means and said one shoe to move the remaining shoessimultaneously inwardly at said rate.

4. A tube pointer as defined in claim 3 in which said camming meansinclude said extensions of said working faces in sliding and cammingengagement with said side surfaces.

5. A tube pointer as defined in claim 1 in which said die has three dieshoes arranged around said recess with said working faces forming anequilateral triangle.

6. A tube pointer as defined in claim 1 in which said die has four dieshoes arranged around said recess with said working faces forming asquare.

7. A tube pointer as defined in claim 1 in which said die has more thanfour die shoes.

8. A tube pointer as defined in claim 1 in which said curved innersurfaces are longitudinal sections of a cylinder and move together toform a cylinderin said closed position.

9. Apparatus for forming a reduced diameter portion on a tube, saidapparatus having, in combination:

at least three die shoes arranged around and defining an open-endedrecess of generally polygonal cross section for receiving the portion ofthe tube to be reduced in diameter;

each of said shoes having a substantially flat inner working faceforming one side of said recess, and said shoes being fitted togetherfor in and out movement in gap-free relation to contract and expand saidrecess in generally polygonal cross-sectional shape;

means on said shoes for changing the shape of said recess from generallypolygonal to generally cylindrical shape as the shoes are moved inwardlyto a selected closed position, whereby the tube first is flattened tosaid generally polygonal shape and then is formed to said generallycylindrical shape; and

means on said shoes for controlling the transition zone of the tubebetween said reduced diameter portion and the remainder of the tube, andincluding an extension of each working face projecting outwardly at oneend of said recess and inclined away from the tube to sink progressivelyinto the transition zone at a selected angle as the recess is contractedin said polygonal cross-sectional shape, and means on said extensionsfor closing around said transition zone in a tapered form of generallycircular cross section as the shape of said recess is changed frompolygonal to cylindrical shape.

10. Apparatus as defined in claim 9 in which said shape-changing meanscomprise a curved inner surface on each of said shoes curving concavelybetween the working face of the shoe on which it is formed and theworking face of the adjacent shoe, whereby said generally polygonalcross section has flat sides joined by curved sections, said curvedsections being moved together to said generally cylindrical shape assaid shoes are moved to said closed position.

11. Apparatus as defined in claim 10 in which each of said extensions isa bevel that is inclined outwardly from one end of the working facethereon toward the open end of said recess, and said means for closingaround. the transition zone comprises a second concavely curved innersurface on each of said shoes between one side of the bevel thereof andthe bevel of the adjacent shoe, said second curved surface being anextension of the first curved surface and generally in the shape of alongitudinal section of a cone.

-l2. Apparatus for forming a reduced-size portion on a tube, saidapparatus having, in combination:

at least three die shoes arranged in alternately overlapped relationaround, and defining, a recess for receiving the portion of the tube tobe reduced in size;

each of said shoes having an inner working face forming one side of saidrecess, a side surface in sliding relation with an extension of theworking face of a first adjacent die shoe, and an extension of itsworking face in sliding relation with the side surface of a secondadjacent die shoe whereby said shoes are movable inwardly from an openposition toward a closed position and then back outwardly to contractand expand said recess in polygonal form;

and means for moving said die shoes simultaneously inwardly at the samerate while a portion of a tube is disposed in said recess, therebyflattening the tube to the shape of said recess and then progressivelyreducing the size of the tube while maintaining the tube and thereduced-size portion coaxial, said moving means comprising an actuatingmember engaging at least one of said die shoes and operable to shiftsaid one shoe inwardly at a selected rate, and camming means. responsiveto movement of said actuating member and said one shoe for shifting allof said shoes inwardly at the same rate as said one shoe thereby tomaintain said reduced size portion constantly positioned on asubstantially stationary longitudinal axis.

13. Apparatus as defined in claim 12 in which each of said shoes has aconcavely curved, inwardly facing surface extending along the side ofits working face which slides along the working face of an adjacentshoe, thereby to form curved sections in the tube between said workingfaces and squeeze said curved sections toward each other as the shoesare moved inwardly, and further including a bevel on each shoe inclinedoutwardly from one end of the working face thereon toward one end ofsaid recess, and a second concavely curved inner surface on each of saidshoes between one side of the bevel thereof and the bevel of theadjacent shoe, said second curved surface being an extension of thefirst curved surface and generally in the shape of a longitudinalsection of a cone.

14. The method of forming a reduced size diameter on one end portion ofa tube, said method including the steps of:

flattening said one end portion from at least three sides thereof toform the tube into a generally polygonal cross section while shaping thetube between the sides of said polygonal cross section into curvedsections;

sinking the tube inwardly in controlled tapered fashion from at leastthree sides in the zone between said one end portion and the remainderof the tube;

squeezing said one end portion to shorten said sides and cause them tobuckle inwardly between said curved sections while moving said curvedsections toward each other;

squeezing said zone toward a tapered form of generally circular crosssection;

and continuing such squeezing and buckling at least until said curvedsections are brought substantially together into a reduced diameterportion and said zone is brought into a tapered form of substantiallycircular cross section.

15. Apparatus as defined in claim 12 including a case having insideguiding surfaces constituting part of said camming means, said actuatingmember forming one movable side of said case and having a V-shaped notchon its inner side forming two of said guiding surfaces, each of said dieshoes having an outer side movable along one of said guiding surfaces,and two of said outer surfaces being slidably engaged by said guidingsurfaces of said actuating member during inward movement thereof, theoverlapped surfaces of said shoes cooperating with said outer sides andsaid guiding surfaces to cam all of said shoes inwardly at the same rateas said actuating member moves inwardly.

16. Apparatus as defined in claim 12 further including means forshifting all of said shoes simultaneously outwardly from said closedposition as saidactuating member moves outwardly.

1. A tube pointer having, in combination: a case; a die mounted in saidcase and comprising at least three die shoes arranged in alternatelyoverlapped relation around, and defining, an open-ended recess forreceiving one end portion of a tube to be pointed; each of said dieshoes having a flat inner working face forming one side of said recess,a side surface in sliding relation with an extension of the working faceof a first adjacent die shoe, and an extension of its working face insliding relation with the side surface of a second adjacent die shoewhereby said shoes are movable simultaneously inwardly from an openposition toward a closed position and then back outwardly toward saidopen position to contract and expand said recess; a bevel on each ofsaid shoes inclined outwardly from the working face thereof toward saidopen end; an elongated first lip extending along the side of eachworking face adjacent the side surface thereof that slides along theworking face of an adjacent block, each of said lips having a curvedinner surface generally tangent to both of the adjacent working facesand curved about the axis of a tube centered in said recess; and asecond lip constituting an extension of said first lip on each of saidshoes along one side of the bevel thereon, each of said second lipshaving an inner surface of generally conical curvature flaring towardsaid open end and generally tangent to both of the adjacent bevels,whereby said die shoes are movable progressively inwardly from said openposition to contract said recess about a tube, bend the tube first to aflattened, generally polygonal cross section with curved sectionsbetween the flattened wall portions, progressively contract the tubepolygonally to cause the flattened wall portions to buckle inwardly, andfinally bring the curved sections together to a substantiallycylindrical point while shaping the tube conically between said secondlips.
 2. A tube pointer as defined in claim 1 further including meansfor moving all of said die shoes simultaneously inwardly at the samerate and maintaining the point on a preselected axis as it is formed. 3.A tube pointer as defined in claim 2 in which said moving means includesactuating means for shifting at least one of said shoes inwardly at aselected rate, and camming means reSponsive to movement of saidactuating means and said one shoe to move the remaining shoessimultaneously inwardly at said rate.
 4. A tube pointer as defined inclaim 3 in which said camming means include said extensions of saidworking faces in sliding and camming engagement with said side surfaces.5. A tube pointer as defined in claim 1 in which said die has three dieshoes arranged around said recess with said working faces forming anequilateral triangle.
 6. A tube pointer as defined in claim 1 in whichsaid die has four die shoes arranged around said recess with saidworking faces forming a square.
 7. A tube pointer as defined in claim 1in which said die has more than four die shoes.
 8. A tube pointer asdefined in claim 1 in which said curved inner surfaces are longitudinalsections of a cylinder and move together to form a cylinder in saidclosed position.
 9. Apparatus for forming a reduced diameter portion ona tube, said apparatus having, in combination: at least three die shoesarranged around and defining an open-ended recess of generally polygonalcross section for receiving the portion of the tube to be reduced indiameter; each of said shoes having a substantially flat inner workingface forming one side of said recess, and said shoes being fittedtogether for in and out movement in gap-free relation to contract andexpand said recess in generally polygonal cross-sectional shape; meanson said shoes for changing the shape of said recess from generallypolygonal to generally cylindrical shape as the shoes are moved inwardlyto a selected closed position, whereby the tube first is flattened tosaid generally polygonal shape and then is formed to said generallycylindrical shape; and means on said shoes for controlling thetransition zone of the tube between said reduced diameter portion andthe remainder of the tube, and including an extension of each workingface projecting outwardly at one end of said recess and inclined awayfrom the tube to sink progressively into the transition zone at aselected angle as the recess is contracted in said polygonalcross-sectional shape, and means on said extensions for closing aroundsaid transition zone in a tapered form of generally circular crosssection as the shape of said recess is changed from polygonal tocylindrical shape.
 10. Apparatus as defined in claim 9 in which saidshape-changing means comprise a curved inner surface on each of saidshoes curving concavely between the working face of the shoe on which itis formed and the working face of the adjacent shoe, whereby saidgenerally polygonal cross section has flat sides joined by curvedsections, said curved sections being moved together to said generallycylindrical shape as said shoes are moved to said closed position. 11.Apparatus as defined in claim 10 in which each of said extensions is abevel that is inclined outwardly from one end of the working facethereon toward the open end of said recess, and said means for closingaround the transition zone comprises a second concavely curved innersurface on each of said shoes between one side of the bevel thereof andthe bevel of the adjacent shoe, said second curved surface being anextension of the first curved surface and generally in the shape of alongitudinal section of a cone.
 12. Apparatus for forming a reduced-sizeportion on a tube, said apparatus having, in combination: at least threedie shoes arranged in alternately overlapped relation around, anddefining, a recess for receiving the portion of the tube to be reducedin size; each of said shoes having an inner working face forming oneside of said recess, a side surface in sliding relation with anextension of the working face of a first adjacent die shoe, and anextension of its working face in sliding relation with the side surfaceof a second adjacent die shoe whereby said shoes are movable inwardlyfrom an open position toward a closed position and then back outwardlyto contract And expand said recess in polygonal form; and means formoving said die shoes simultaneously inwardly at the same rate while aportion of a tube is disposed in said recess, thereby flattening thetube to the shape of said recess and then progressively reducing thesize of the tube while maintaining the tube and the reduced-size portioncoaxial, said moving means comprising an actuating member engaging atleast one of said die shoes and operable to shift said one shoe inwardlyat a selected rate, and camming means responsive to movement of saidactuating member and said one shoe for shifting all of said shoesinwardly at the same rate as said one shoe thereby to maintain saidreduced size portion constantly positioned on a substantially stationarylongitudinal axis.
 13. Apparatus as defined in claim 12 in which each ofsaid shoes has a concavely curved, inwardly facing surface extendingalong the side of its working face which slides along the working faceof an adjacent shoe, thereby to form curved sections in the tube betweensaid working faces and squeeze said curved sections toward each other asthe shoes are moved inwardly, and further including a bevel on each shoeinclined outwardly from one end of the working face thereon toward oneend of said recess, and a second concavely curved inner surface on eachof said shoes between one side of the bevel thereof and the bevel of theadjacent shoe, said second curved surface being an extension of thefirst curved surface and generally in the shape of a longitudinalsection of a cone.
 14. The method of forming a reduced size diameter onone end portion of a tube, said method including the steps of:flattening said one end portion from at least three sides thereof toform the tube into a generally polygonal cross section while shaping thetube between the sides of said polygonal cross section into curvedsections; sinking the tube inwardly in controlled tapered fashion fromat least three sides in the zone between said one end portion and theremainder of the tube; squeezing said one end portion to shorten saidsides and cause them to buckle inwardly between said curved sectionswhile moving said curved sections toward each other; squeezing said zonetoward a tapered form of generally circular cross section; andcontinuing such squeezing and buckling at least until said curvedsections are brought substantially together into a reduced diameterportion and said zone is brought into a tapered form of substantiallycircular cross section.
 15. Apparatus as defined in claim 12 including acase having inside guiding surfaces constituting part of said cammingmeans, said actuating member forming one movable side of said case andhaving a V-shaped notch on its inner side forming two of said guidingsurfaces, each of said die shoes having an outer side movable along oneof said guiding surfaces, and two of said outer surfaces being slidablyengaged by said guiding surfaces of said actuating member during inwardmovement thereof, the overlapped surfaces of said shoes cooperating withsaid outer sides and said guiding surfaces to cam all of said shoesinwardly at the same rate as said actuating member moves inwardly. 16.Apparatus as defined in claim 12 further including means for shiftingall of said shoes simultaneously outwardly from said closed position assaid actuating member moves outwardly.